I installed my fuel pressure gauge this afternoon, pretty easy and no problems installing it. Turn the truck on, and the pressure gague needle pegged itself on 30 psi. That didnt seem right, figured something with the gauge. Tried a couple different things and it still read 30 psi. So i called airdog and asked them if that is to much fuel pressure and they said yes. They are going to send me a new spring. So i talked to the guy and asked him if there was any reason for seeing such a high FP and he told me to make sure my return line was free of kinks ect which is was, said i could trim a half of ring off the spring and put it back in, which i did with no effect, third he told me to dissconnect the return line and put it into a bucket and then check the fuel pressure which i did, and then wam, the gauge was reading
~15psi. I called him back and told him and he said that i have a restirction in the return line somewhere and that is causing my fuel pressure to be to high. I checked over all the return line and there was nothing kinked or anything. Only thing left to check was the canister in the tank. I have a 1/2" to 3/8" dorman adapter that i bought with my drawstraw VHF and the purpose of this is to use your stock pick up line as the return line for the airdog. Anyways, when i installed the drawstraw, i had cut the stock pick up line where it connected to the fuel pump and left the rest in place. So i got to thinking that it might be possible that my return line ( the stock pick tube) maybe sumbereged in fuel all the time thus causing a "back up"/ restriction. However when all this was happening, my fuel light was on and there was little fuel in the tank. So, i disconected the return line and used the filler neck adapter piece and used that as the return line and now my readings are good. With the fuel light on, i was reading ~15psi and with the fuel sloshing around the lowest i ever saw was ~8psi, mostly when the truck is facing down hill or coming to a stop, never saw 0psi. One final thing, i went and filled the truck up and now i am getting 21psi with only a psi or two in fluctuation when driving.
Sorry for the long post, anyone have any insight on why i was having 30psi + reading with the return line going back into the canister? Thanks for the help

 

I'd thinking the restriction is at the canister. The stock feed is 3/8 but there's a major restriction where the tube 90*s at the top of the canister, it narrows down to ¼" there, that's your problem.

You do not want want your AD return plumbed into the filler neck, if you draw from the canister you need to dump the AD return there as well or you'll have problems when you get down to less that 3/8 of a tank like I did, see my signature.
If you're drawing from a draw straw in the tank itself you'll be okay dumping the return into the filler neck, but of course there's always the chance you're draw straw will be too short and you'll have problems when you get down around ¼ tank, some people do get it just right though.


I was reading about the new AD2's, they're sposed to be designed so some of the AD return is returned internally somehow so there's not the flow we had with our old ones. They say with the new AD2's you're okay plumbing the return to the stock 3/8" feed line.

Is yours an old style like my AD100 or the new AD2?

 

I was hoping you would respond, you seem to know the ins and outs of these pumps, probably not by choice though, haha. I dont believe that mine is the AD2, just the Airdog 150 which is about 4 months old. I never thought about the tight 90* bend at the top of the canister where the 3/8" line is. Well unfortunatly i used the piece that returns through the filler neck cause i didnt know if having such high FP could damage the airdog or my cp3. So my draw straw is going to drain the canister before it is able to fill back up with fuel now that i have the return line plumbed other than the canister? I did drill a couple of holes in the sides of the canister in hopes that fuel would flow through them and help maintain the level in the canister. I really dont want to take the bed off again, not that it was difficult, just dont like setting it back on and worrying about banging it up. What are you seeing for FP readings? Thanks for your help

 

Mine's a steady 16 psi no matter how low my tank is, it'll drop to like 15 when I really get into it.

Later AD sent me 4 springs, the 20 lb spring gave me pegged my gauge at 30 pounds so I never even tried the 25 pound. If you want more just pull out the spring and stretch it a little. 15-16 is fine though and really all you need.

So you're pulling from a new draw straw in the canister, so I think you'll hafta pull the canster out to add another draw straw for the AD return, or buy one of the kits available now. 53Willy's was selling pre done ones for a while, not sure if he still is though.

Sucks I know, good luck.
Will

 

yeah, it does suck, i was stoked when i was searching for drawstraws when Vulcan had the 1/2" to 3/8" dorman adapter so you could use the stock pickup line for the Airdog return. I do have a draw straw in the canister, but the return line has been moved to the filler neck because of the fuel pressure issue. Not sure what i am going to do, could it be possible to utlize the draw straw that came with the kit and put that in the canister as the return and just trim the lenght of it down some? Just trying to save myself from buying more items.

 

Yup, that's what I'd do.

 

Ok, well thanks for all your help, guess i will have to find time to take the bed off or drop the tank one of these days, not looking forward to it but i want it to be right. Some times i wish i was not so picky about things